Papers by Bruno R S Figueiredo
The processes that determine the coexistence of phylogenetically close species are very complex, ... more The processes that determine the coexistence of phylogenetically close species are very complex, particularly when species introduction leads to sympatry among species that did not co-evolved. We evaluated possible differences in δ13C and δ15N signatures between two piranha species (Serrasalmus marginatus and S. maculatus), in a system where S. marginatus invaded 30 years ago (floodplain ponds in the Upper Paraná River). We predicted that carbon and nitrogen stable isotope values would not differ between piranha species. Additionally, we evaluated the abundance (CPUE) of both piranha populations along the years (1986-2015). Native and non-native Serrasalmus species have different δ13C signatures, likely exploiting different energy pathways on the food web. Overall, native and non-native piranha have similar δ15N values and occupy the third trophic level in the food web. Regarding the two piranha population fluctuations, there was an inversion of dominance after the non-native species establishment, where S. marginatus became dominant over S. maculatus (after 1988). Our results showed that trophic niche dimension (revealed by trophic segregation) is not the reason of the observed inversion in the dominant species, and this could be a primary factor driving the persistence of the native species in the ecosystem.
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1. In aquatic systems, many species rely primarily on visual cues to choose optimal foraging site... more 1. In aquatic systems, many species rely primarily on visual cues to choose optimal foraging sites, capture prey and avoid potential threats. Increases in the turbidity of water reduce visibility and impede animals in determining the precise location of both predators and food. How individuals balance foraging decisions with anti-predator behaviour in turbid environments is not well understood.
2. Here, we tested the effects of turbidity and predation risk on the foraging behaviour and feeding of invertivorous fish (Moenkhausia forestii (Characidae)) using a mesocosm experiment with a 2x2 design, crossing water clarity (clear vs. turbid) with predation risk (absence vs. presence of the piscivorous wolf-fish Hoplias aff. malabaricus (Erythrinidae)). We predicted that turbidity and predator presence interact additively to reduce foraging rate, and that increased turbidity or predator presence result in disproportionate food partitioning among shoal members.
3. The combination of high turbidity and predator presence resulted in a significant reduction in prey consumption. Foraging success exhibited a skewed distribution in the turbid treatment, i.e. there was a decreased evenness of food partitioning within shoals. Hence, both turbidity and predator presence affect the prey consumption and foraging behaviour of invertivorous fish, with turbidity amplifying the non-lethal effects of predation risk on foraging success.
4. Our results imply that turbidity-induced visual obstruction amplifies the negative effects of predator presence on invertivorous fish feeding behaviour, resulting in higher prey survival. Also, our finding that food intake by an intermediate consumer decreased in turbid water with a top predator lends no support to the hypothesis that intermediate consumer fish reduce their anti-predator behaviour in turbid water.
5. From a management perspective, our findings suggest that the oligotrophication of aquatic systems could (i) dramatically increase predation on basal prey organisms naturally adapted to turbid waters, and (ii) reduce within-shoal differences in feeding behaviour.
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Resource partitioning has been recognized as a major driver affecting fish communities, with the ... more Resource partitioning has been recognized as a major driver affecting fish communities, with the potential to reduce interespecific competition. This is the result of differences in feeding apparatuses and feeding mode, location of the fish species in the water column and swimming ability, as well as type and size of prey and its availability. The present study surveys a highly limited aquatic system in semi-arid Brazil with regard to habitat and food availability, with very low diversity of fish, and poor in underwater habitat structures and prey, with the objective of understanding resource partitioning among fish species under such conditions. Three species of Cichlidae (Pisces: Perciformes) were sampled during the dry and wet seasons and had their stomach contents analyzed to evaluate food consumption. The resource partition among fish species was evaluated based on Pianka’s niche overlap index and tested for significance against null models. It was observed a low overlap among the study species in food resource use, with individuals tending to specialize to select some food items. This is likely the result of low natural variation in abundance of specific food items associated with fish preferences (both morphological and behavioral). These results support evidence that, in Brazilian semi-arid aquatic systems, coexistence of fish species seems to be enhanced by the partition of food items at specific trophic levels. Within this context, flow variability would have a key hole in fish coexistence by promoting a high diversity of aquatic habitat elements available for colonization of fish and their prey. Furthermore, food resources available to fish play an important role in this dynamics since prey foods are expected to vary in abundance as the habitat changes.
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In this study, we tested the hypothesis that in floodplain lakes connected to a primary river wi... more In this study, we tested the hypothesis that in floodplain lakes connected to a primary river with regulated flow, the zooplankton composition is maintained by the species found in lakes connected to preserved tributaries (under the influence of damming). Zooplankton were sampled from 23 lakes connected to the Paraná, Ivinhema and Baía Rivers on the floodplain of the Upper Paraná River. For this purpose, we evaluated zooplankton α, β and γ diversity and applied dispersal analysis to identify the dispersal of species among lakes. In addition, we investigated whether the Baía and Ivinhema Rivers could disperse species to the Paraná River Basin through an analysis of source environments. A total of 150 species were observed, and the greatest number of species (115 species) occurred in environments associated with the flow-regulated Paraná River. Dispersal of species among all lakes was identified. The highest α-diversity values were found in the environments connected to the tributaries, the Ivinhema and Baía Rivers, which also contributed more than 50% of the composition of the lakes associated with the Paraná River. There was also greater β-diversity in these environments, where the composition was significantly correlated with turbidity, chlorophyll-a and conductivity. The results supported our hypothesis and showed that when the main river is regulated by a dam, the tributaries take on the role of maintaining γ-diversity in the floodplain, favouring the maintenance of the natural characteristics of the system. We propose that preserving the integrity of natural floodplain environments assists in maintaining the regional diversity of the ecosystem as a whole
Zooplankton diversity in a dammed river basin is maintained by preserved tributaries in a tropical floodplain. Available from: https://www.researchgate.net/publication/274720873_Zooplankton_diversity_in_a_dammed_river_basin_is_maintained_by_preserved_tributaries_in_a_tropical_floodplain [accessed Apr 20, 2015].
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Aquatic macrophytes colonize a variety of environments,
and they play important roles in ecosyste... more Aquatic macrophytes colonize a variety of environments,
and they play important roles in ecosystem
function and in community structure. One key challenge
for aquatic ecologists is to investigate the environmental
factors that drive the richness and distribution of these
plants. In this study, we assessed the importance of selected
morphometric variables and of the canopy openness of the
riparian vegetation to explain macrophyte species richness
and composition. We sampled macrophytes along gradients
of depth, littoral slope, distance from the connection with
the river, and canopy openness in floodplain lakes connected
with the Upper Parana´ River. We used quadrats to
survey a total of 40 sites in 11 lakes. We recorded 31
macrophyte species and found that macrophyte richness
was best and positively correlated with canopy openness.
This correlation suggests that canopy openness plays an
important role as an environmental filter, regulating the
amount of light availability for macrophytes. Macrophyte
species composition was best correlated with depth, indicating
that zonation of macrophyte species also occurs in
these shallow lakes. These findings emphasize the importance
of morphometric variables and canopy openness for
structuring macrophyte assemblages. In addition, our results
suggest that canopy openness and depth may be
considered in management strategies aiming to recover
macrophyte diversity and the processes mediated by
aquatic macrophytes in small and shallow floodplain lakes.
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Bottom-feeding fish show great variation in trophic morphology, resulting in a wide array of feed... more Bottom-feeding fish show great variation in trophic morphology, resulting in a wide array of feeding habits exploiting from periphyton in littoral habitats to ingesting larger amounts of litterfall from terrestrial habitats. Nevertheless, it has been proposed that, in temperate aquatic systems, the energetic demands from bottom-feeding fish are supplied by primary production from phytoplankton in pelagic habitats. Thus, we aimed to determine which of several energy sources support bottom-feeding fish in tropical aquatic systems, where
primary producers are diverse.We performed samplings in the Paraná River floodplain from primary producers in littoral (periphyton), pelagic (phytoplankton) and terrestrial habitats (riparian vegetation). Using simultaneous signatures of C and N isotope ratios, we analysed the possible origin of available energy in muscles of nine different bottom-feeding fish species. We verified that seven of the nine fish species had the highest contribution of carbon from a littoral source compared to other energy sources, independent of trophic category. The importance of periphyton may be related to the high abundance of substrates (such as macrophytes) that are available in the littoral zone of tropical aquatic systems. Finally, we suggest that the actual carbon dynamics among bottom-feeding fish and primary producers is species-specific, varying within the same trophic guild, and therefore, it is possible to refute the assumption that each trophic guild is specialised for a distinct carbon source.
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Papers by Bruno R S Figueiredo
2. Here, we tested the effects of turbidity and predation risk on the foraging behaviour and feeding of invertivorous fish (Moenkhausia forestii (Characidae)) using a mesocosm experiment with a 2x2 design, crossing water clarity (clear vs. turbid) with predation risk (absence vs. presence of the piscivorous wolf-fish Hoplias aff. malabaricus (Erythrinidae)). We predicted that turbidity and predator presence interact additively to reduce foraging rate, and that increased turbidity or predator presence result in disproportionate food partitioning among shoal members.
3. The combination of high turbidity and predator presence resulted in a significant reduction in prey consumption. Foraging success exhibited a skewed distribution in the turbid treatment, i.e. there was a decreased evenness of food partitioning within shoals. Hence, both turbidity and predator presence affect the prey consumption and foraging behaviour of invertivorous fish, with turbidity amplifying the non-lethal effects of predation risk on foraging success.
4. Our results imply that turbidity-induced visual obstruction amplifies the negative effects of predator presence on invertivorous fish feeding behaviour, resulting in higher prey survival. Also, our finding that food intake by an intermediate consumer decreased in turbid water with a top predator lends no support to the hypothesis that intermediate consumer fish reduce their anti-predator behaviour in turbid water.
5. From a management perspective, our findings suggest that the oligotrophication of aquatic systems could (i) dramatically increase predation on basal prey organisms naturally adapted to turbid waters, and (ii) reduce within-shoal differences in feeding behaviour.
Zooplankton diversity in a dammed river basin is maintained by preserved tributaries in a tropical floodplain. Available from: https://www.researchgate.net/publication/274720873_Zooplankton_diversity_in_a_dammed_river_basin_is_maintained_by_preserved_tributaries_in_a_tropical_floodplain [accessed Apr 20, 2015].
and they play important roles in ecosystem
function and in community structure. One key challenge
for aquatic ecologists is to investigate the environmental
factors that drive the richness and distribution of these
plants. In this study, we assessed the importance of selected
morphometric variables and of the canopy openness of the
riparian vegetation to explain macrophyte species richness
and composition. We sampled macrophytes along gradients
of depth, littoral slope, distance from the connection with
the river, and canopy openness in floodplain lakes connected
with the Upper Parana´ River. We used quadrats to
survey a total of 40 sites in 11 lakes. We recorded 31
macrophyte species and found that macrophyte richness
was best and positively correlated with canopy openness.
This correlation suggests that canopy openness plays an
important role as an environmental filter, regulating the
amount of light availability for macrophytes. Macrophyte
species composition was best correlated with depth, indicating
that zonation of macrophyte species also occurs in
these shallow lakes. These findings emphasize the importance
of morphometric variables and canopy openness for
structuring macrophyte assemblages. In addition, our results
suggest that canopy openness and depth may be
considered in management strategies aiming to recover
macrophyte diversity and the processes mediated by
aquatic macrophytes in small and shallow floodplain lakes.
primary producers are diverse.We performed samplings in the Paraná River floodplain from primary producers in littoral (periphyton), pelagic (phytoplankton) and terrestrial habitats (riparian vegetation). Using simultaneous signatures of C and N isotope ratios, we analysed the possible origin of available energy in muscles of nine different bottom-feeding fish species. We verified that seven of the nine fish species had the highest contribution of carbon from a littoral source compared to other energy sources, independent of trophic category. The importance of periphyton may be related to the high abundance of substrates (such as macrophytes) that are available in the littoral zone of tropical aquatic systems. Finally, we suggest that the actual carbon dynamics among bottom-feeding fish and primary producers is species-specific, varying within the same trophic guild, and therefore, it is possible to refute the assumption that each trophic guild is specialised for a distinct carbon source.
2. Here, we tested the effects of turbidity and predation risk on the foraging behaviour and feeding of invertivorous fish (Moenkhausia forestii (Characidae)) using a mesocosm experiment with a 2x2 design, crossing water clarity (clear vs. turbid) with predation risk (absence vs. presence of the piscivorous wolf-fish Hoplias aff. malabaricus (Erythrinidae)). We predicted that turbidity and predator presence interact additively to reduce foraging rate, and that increased turbidity or predator presence result in disproportionate food partitioning among shoal members.
3. The combination of high turbidity and predator presence resulted in a significant reduction in prey consumption. Foraging success exhibited a skewed distribution in the turbid treatment, i.e. there was a decreased evenness of food partitioning within shoals. Hence, both turbidity and predator presence affect the prey consumption and foraging behaviour of invertivorous fish, with turbidity amplifying the non-lethal effects of predation risk on foraging success.
4. Our results imply that turbidity-induced visual obstruction amplifies the negative effects of predator presence on invertivorous fish feeding behaviour, resulting in higher prey survival. Also, our finding that food intake by an intermediate consumer decreased in turbid water with a top predator lends no support to the hypothesis that intermediate consumer fish reduce their anti-predator behaviour in turbid water.
5. From a management perspective, our findings suggest that the oligotrophication of aquatic systems could (i) dramatically increase predation on basal prey organisms naturally adapted to turbid waters, and (ii) reduce within-shoal differences in feeding behaviour.
Zooplankton diversity in a dammed river basin is maintained by preserved tributaries in a tropical floodplain. Available from: https://www.researchgate.net/publication/274720873_Zooplankton_diversity_in_a_dammed_river_basin_is_maintained_by_preserved_tributaries_in_a_tropical_floodplain [accessed Apr 20, 2015].
and they play important roles in ecosystem
function and in community structure. One key challenge
for aquatic ecologists is to investigate the environmental
factors that drive the richness and distribution of these
plants. In this study, we assessed the importance of selected
morphometric variables and of the canopy openness of the
riparian vegetation to explain macrophyte species richness
and composition. We sampled macrophytes along gradients
of depth, littoral slope, distance from the connection with
the river, and canopy openness in floodplain lakes connected
with the Upper Parana´ River. We used quadrats to
survey a total of 40 sites in 11 lakes. We recorded 31
macrophyte species and found that macrophyte richness
was best and positively correlated with canopy openness.
This correlation suggests that canopy openness plays an
important role as an environmental filter, regulating the
amount of light availability for macrophytes. Macrophyte
species composition was best correlated with depth, indicating
that zonation of macrophyte species also occurs in
these shallow lakes. These findings emphasize the importance
of morphometric variables and canopy openness for
structuring macrophyte assemblages. In addition, our results
suggest that canopy openness and depth may be
considered in management strategies aiming to recover
macrophyte diversity and the processes mediated by
aquatic macrophytes in small and shallow floodplain lakes.
primary producers are diverse.We performed samplings in the Paraná River floodplain from primary producers in littoral (periphyton), pelagic (phytoplankton) and terrestrial habitats (riparian vegetation). Using simultaneous signatures of C and N isotope ratios, we analysed the possible origin of available energy in muscles of nine different bottom-feeding fish species. We verified that seven of the nine fish species had the highest contribution of carbon from a littoral source compared to other energy sources, independent of trophic category. The importance of periphyton may be related to the high abundance of substrates (such as macrophytes) that are available in the littoral zone of tropical aquatic systems. Finally, we suggest that the actual carbon dynamics among bottom-feeding fish and primary producers is species-specific, varying within the same trophic guild, and therefore, it is possible to refute the assumption that each trophic guild is specialised for a distinct carbon source.